I don't think he said they all sound the same, he said they all sound great. And it was just an encouraging remark to RolandPSP at that.
Mh...I'm sorry but I don't get it which one of these should be matched. Could someone help me? I'm a bit confused. Thx in advance.
Anyone have pcb's to purchase?
It is nice to see people still building this amplifier, and I can say that it really is the most appealing circuit design over all... other than the complexity and mass amount of parts used due to all the constant current sources, must look like christmas! I am particularly attracted to the fact of avoiding coupling caps and using a J-FET LTP.
I am curious about either purchasing some boards or making my own using the same component layout but having all of the output transistors on one side of the board so as to be sure to fit the heat sinks I have (H100mm L275mm W50mm) I would be using two of these heatsinks... maybe the boards will fit as is now but also makes them easier to work with if you have to change out any components.
Finding some of these transistors might be fun... unless I take my chances with some of the used ones I have. (I know my user name doesn't do me any justice, maybe I can try some good ol thermionics in place of the transistors I have trouble finding
)
Alan
It is nice to see people still building this amplifier, and I can say that it really is the most appealing circuit design over all... other than the complexity and mass amount of parts used due to all the constant current sources, must look like christmas! I am particularly attracted to the fact of avoiding coupling caps and using a J-FET LTP.
I am curious about either purchasing some boards or making my own using the same component layout but having all of the output transistors on one side of the board so as to be sure to fit the heat sinks I have (H100mm L275mm W50mm) I would be using two of these heatsinks... maybe the boards will fit as is now but also makes them easier to work with if you have to change out any components.
Finding some of these transistors might be fun... unless I take my chances with some of the used ones I have. (I know my user name doesn't do me any justice, maybe I can try some good ol thermionics in place of the transistors I have trouble finding
)Alan
Just finished the left channel - point to point wired. Splendid device really great. Thx to Mihai and also to Rudi for further informations (Shunt PSU etc).
Btw interessting Frontend-PSU Upgrade http://www.diyaudio.com/forums/power-supplies/293758-lt3062-based-psu.html did anyone tried to use a LDO?
really great. Thx to Mihai and also to Rudi for further informations (Shunt PSU etc). Btw interessting Frontend-PSU Upgrade http://www.diyaudio.com/forums/power-supplies/293758-lt3062-based-psu.html did anyone tried to use a LDO?
Actually I'm facing some minor Problems with some harsh trebles. Compared to my Symasym the FC-100 sounds a bit harsh when it comes to high-pitched vocals, violins etc. Everything else is more than perfect (Stage, bass etc.).
I've built the amplifier point to point wired on a pcb with 70um copper. Base layout is the same as mentioned in Rudis Build thread.
Two things came in my mind which might cause this behavior and I want to ask if I'm on the right track.
1. hfe of the NJL0281/NJL0302 differ around 50%(93/130) 0281vs0302. VBE around 1%. Within 0281 everything below 1% - same for 0302.
MJE15030/15031 hfe (100%) but VBE < 5%.
anything else is matched <1%
DC offset is 0,7mV (left) and 1,4 mV (right)
2.NFB. Due to my "ugly style wiring" there might be an issue with the NFB wire. I tried to keep the wire as close as possible to the groundplane but maybe it is to long/short (but tried to fit the original design) or it picks up some stuff surrounding it.
3...just a maybe. Groundplanes (left/right channels) aren't attached to the case - so no "global" earth. Symasym is earth grounded.
it would be nice I someone could tell me his thoughts on this - so that I might investigate into the right direction.
Thx in advance
Alex
I've built the amplifier point to point wired on a pcb with 70um copper. Base layout is the same as mentioned in Rudis Build thread.
Two things came in my mind which might cause this behavior and I want to ask if I'm on the right track.
1. hfe of the NJL0281/NJL0302 differ around 50%(93/130) 0281vs0302. VBE around 1%. Within 0281 everything below 1% - same for 0302.
MJE15030/15031 hfe (100%) but VBE < 5%.
anything else is matched <1%
DC offset is 0,7mV (left) and 1,4 mV (right)
2.NFB. Due to my "ugly style wiring" there might be an issue with the NFB wire. I tried to keep the wire as close as possible to the groundplane but maybe it is to long/short (but tried to fit the original design) or it picks up some stuff surrounding it.
3...just a maybe. Groundplanes (left/right channels) aren't attached to the case - so no "global" earth. Symasym is earth grounded.
it would be nice I someone could tell me his thoughts on this - so that I might investigate into the right direction.
Thx in advance
Alex
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I don't want to discourage you, but there are almost zero chances to make this amp sound correctly by using point to point assembly method.
Why don't you buy PCBs from Rudi?
http://www.diyaudio.com/forums/group-buys/293550-roenders-fc-100-group-buy.html
I had a problems with mk ii ver of this amp as well, there were serious oscillations in the circuit, however i used toshiba op devices and bf862 jfets. I was able to solve the problems only by changing 150R to 33R and installing a 15pF compensation caps on drivers.
Mihai, is there a rule of choosing those resistor optimal values for drivers bias current?
Mihai, is there a rule of choosing those resistor optimal values for drivers bias current?
Hi guys,
not so active theme unfortunately, but...
I'm in process to building FC-100. Have a luck to find PCB kit and matched some important transistors.
Now collecting other parts and hardware stuff
So I have a question about some very important (by my POV) parts:
What is your choice for R23, 24 in NFB and input resistor R27? I think that they have a big influence of sound....
In a first look, my choice will be Z-Foil resistors... (I will try my best to afford)
The same question are for C21?
Unfortunately not so much space left on PCB for good enough capacitor (what a word - "good enough")
Thinking to use AudioNote Kaisei 470uF/25V, wish is a little big for this...
Any recommendation from your past experience? I think that my question are valid in general, not only for FC-100.
not so active theme unfortunately, but...
I'm in process to building FC-100. Have a luck to find PCB kit and matched some important transistors.
Now collecting other parts and hardware stuff
So I have a question about some very important (by my POV) parts:
What is your choice for R23, 24 in NFB and input resistor R27? I think that they have a big influence of sound....
In a first look, my choice will be Z-Foil resistors... (I will try my best to afford)
The same question are for C21?
Unfortunately not so much space left on PCB for good enough capacitor (what a word - "good enough"
) Thinking to use AudioNote Kaisei 470uF/25V, wish is a little big for this...
Any recommendation from your past experience? I think that my question are valid in general, not only for FC-100.
